1. Field of the Invention
The present invention relates to alkylated N-alkyl-N′-phenyl-p-phenylenediamines. More particularly, the present invention relates to a method for the ring alkylation of N-alkyl-N′-phenyl-p-phenylenediamines.
2. Description of Related Art
Aromatic amines are useful in a broad range of applications. For example, they are antiknock agents in gasoline used in spark ignited internal combustion engines. They are also valuable intermediates in the dye industry and are beneficial when added to rubber, where they prevent degradation caused by ozone.
N-substituted-N′-p-phenylenediamines are also known to be useful in the production of drugs, agricultural products, and as dyes, antioxidants, antiozonants, gel inhibitors, and polymerization inhibitors for rubber.
Methods of orthoalkylating aromatic amines, such as aniline, are known. Suitable methods are disclosed in U.S. Pat. No. 2,762,845; U.S. Pat. No. 2,814,646; and U.S. Pat. No. 3,275,690.
U.S. Pat. No. 2,762,845 discloses a procedure for production of alkylated aromatic amines by reaction of aromatic amines and olefins, the procedure being characterized in that aluminum or aluminum alloys can be used to catalyze the alkylation reaction.
U.S. Pat. No. 2,814,646 discloses reacting aromatic amines, having at least one hydrogen on the amino nitrogen and also having at least one hydrogen on a nuclear carbon atom ortho to the amino nitrogen group, with an organic compound possessing one or more units of carbon-to-carbon unsaturation in the presence of an aluminum anilide-type catalyst.
U.S. Pat. No. 3,275,690 discloses the nuclear alkylation of an aromatic amine by reacting an olefin of the group aliphatic olefins and cycloolefins with a aromatic amine at a temperature of about 150-400° C. in the presence of a Friedel-Crafts catalyst.
U.S. Pat. No. 3,649,693 discloses the selective ortho-alkylation of aromatic amines such as aniline with an olefin in the presence of an aluminum anilide catalyst. The orthoalkylated product is distilled from the reaction mixture without prior hydrolysis and the residue remaining can be recycled as the catalyst for a subsequent orthoalkylation process.
U.S. Pat. Nos. 3,654,331 and 3,923,892 disclose the selective ortho-alkylation of aromatic amines having a hydrogen atom on at least one nuclear carbon atom ortho to an amine group (e.g., aniline) by adding a catalytic amount of an alkyl aluminum halide, such as diethyl aluminum chloride to the aromatic amine and then heating the resultant mixture to about 100-500° C. in the presence of an olefin. The process may also be carried out in the added presence of an aluminum anilide.
U.S. Pat. No. 5,371,289 discloses a process for the preparation of a N-substituted-N′-phenyl-p-phenylenediamine comprising reacting (a) a mixture of (1) N-phenyl-p-quinoneimine and (2) p-hydroxydiphenylamine in a mole ratio of N-phenyl-p-quinoneimine to p-hydroxydiphenylamine of from 1.5:1 to 1:1.5 with (b) a primary amine in the presence of methanol.
The disclosures of the foregoing are incorporated herein by reference in their entirety.